The present invention generally relates to a semiconductor device having a silicide contact structure in which a semiconductor silicon material, an interlayer insulating film with contact holes and a conductive film are laminated in that order, and in which the silicon and the conductive film are connected through the silicide formed within the contact holes, and particularly relates to a semiconductor device and method of fabrication thereof suited to prevent the silicide and the silicon from being peeled off from each other.
Recently, the semiconductor device has been integrated at high density and greatly reduced in its size, and each part of the semiconductor device has been strongly desired to be improved in its performance. For example, in order to achieve fast operation, it is required to reduce the contact resistance of the junction between the metal wiring conductor of a conductive film and the semiconductor silicon.
The conventional technique for reducing the resistance of the contact portion that electrically connects the surface of the silicon substrate and the metal wiring conductor is described in Japanese Patent Laid-open Gazette No. 07-078821. This gazette discloses the titanium silicide film that is formed between the silicon substrate and the metal wiring conductor which is to be formed over the substrate.
It is known by experience that in order to produce a low contact resistance by forming the titanium silicide film in the interface between the silicon and the metal, the thickness of the titanium silicide (TiSix, X≦2) film must be increased to a certain extent. On the contrary, as the thickness of the titanium silicide film is increased, the titanium silicide film is more easily peeled off from the silicon at the interface. Since the titanium silicide film is formed by heating a titanium film after being deposited on the silicon in order to cause a reaction between the silicon and the titanium, a stress is generated within the film by the volume change of the film at the time of the reaction. This stress will cause the above exfoliation.
The stress generated within this titanium silicide film also causes a high stress to be generated around the interface between the titanium silicide film and the silicon. This high stress is increased as the titanium silicide film becomes thicker, and as the stress (the internal stress generated after the formation of the conductive film) within the conductive film in contact with the titanium silicide film becomes greater. The great stress generated around the interface between the titanium silicide film and the silicon causes the titanium silicide film to be peeled off from the silicon.
In other words, the titanium silicide film is more easily peeled off as its thickness is increased, and this fact interferes with the high-density integration and great size-reduction of the semiconductor device.